1. Field of the Disclosure
The present invention relates to a display device, and more particularly, to a display device, in which a gamma voltage generator is equipped in a data driver integrated circuit (IC), and a method of driving the same.
2. Background of the Related Art
A flat panel display (FPD) device is applied to various electronic devices such as portable phones, tablet personal computers (PCs), notebook computers, monitors, etc. Examples of the FPD device include liquid crystal display (LCD) devices, plasma display panel (PDP) devices, organic light emitting display devices, etc. Recently, electrophoretic display (EPD) devices are being widely used as one type of the FPD device.
In such FPD devices, LCD devices are devices that display an image using the optical anisotropy of liquid crystal. The LCD devices have a thin thickness, a small size, and low power consumption, and realize a high-quality image.
Among the display devices, organic light emitting display devices are self-emitting devices that self-emit light, and thus have a fast response time, high emission efficiency, high luminance, and a broad viewing angle.
An organic light emitting diode (OLED) configuring the organic light emitting display device includes an anode formed of indium tin oxide (ITO), a hole injection layer stacked on the anode, a hole transport layer stacked on the hole injection layer, an emission material layer stacked on the hole transport layer, an electron transport layer stacked on the emission material layer, an electron injection layer stacked on the electron transport layer, and a cathode stacked on the electron injection layer. Here, each of the hole transport layer, the emission material layer, and the electron transport layer is an organic thin film formed of an organic compound.
When a voltage is applied between the anode and the cathode, a positive hole injected from the anode moves to the emission material layer via the hole transport layer, and an electron injected from the cathode moves to the emission material layer via the electron transport layer. Carriers, such as the positive hole and the electron, are recombined in the emission material layer to generate an exciton. The exciton is shifted from an excited state to a ground state to emit light.
FIG. 1 is an exemplary diagram schematically illustrating a configuration of a related art display device. FIG. 2 is an exemplary diagram schematically illustrating configurations of two data driver ICs configuring the display device of FIG. 1.
The related art display device, as illustrated in FIG. 1, includes a panel 10 in which a plurality of pixels are respectively formed in a plurality of intersection areas between a plurality of data lines and a plurality of gate lines, a data driver IC (D-IC) that respectively supplies data voltages to the data lines, a gate driver (not shown) that supplies a scan signal to the gate lines, and a timing controller (not shown) that drives the data driver IC (D-IC) and the gate driver (not shown).
The data driver IC (D-IC) converts digital image data, transferred from the timing controller, into data voltages, and respectively supplies the data voltages for one horizontal line to the data lines at every one horizontal period in which the scan signal (a gate-on signal) is supplied to a corresponding gate line.
The data driver IC (D-IC) converts the image data into the data voltages by using gamma voltages supplied from a gamma voltage generator, and respectively supplies the data voltages to the data lines.
Only one the data driver IC may be equipped in the display device, but when a width of the panel 10 is long, as illustrated in FIG. 1, two the data driver ICs D-IC#1 and D-IC#2 may be equipped in the panel 10.
For example, when 5760 (=1920×3) pixels are formed on one horizontal line of the panel 10, each of the two data driver ICs respectively supplies data voltages to 2880 data lines.
Each of the two data driver ICs D-IC#1 and D-IC#2, as illustrated in FIG. 2, includes a shift register 31, a latch 32, a digital-to-analog converter (DAC) 33, a gamma voltage generator 35, and an output buffer 34.
When the gamma voltage generator 35 transfers generated gamma voltages to the DAC 33, the DAC 33 selects gamma voltages, respectively corresponding to 2880 pieces of image data transferred from the latch 32, from among the generated gamma voltages, and generates 2880 data voltages respectively corresponding to the 2880 pieces of image data. The generated 2880 data voltages are respectively supplied to the data lines through the output buffer 34.
In FIGS. 1 and 2, the two data driver ICs are used for respectively supplying the data voltages to the data lines formed in one the panel 10. However, three or more of the data driver ICs may be used depending on a size and resolution of the panel 10.
As described above, when two or more the data driver ICs are used for driving the data lines formed in one the panel 10, the same gamma voltage cannot be generated due to a deviation between the data driver ICs. A gamma voltage deviation between the data driver ICs affects a quality of an image output from the panel 10.
For example, as illustrated in FIGS. 1 and 2, when the two data driver ICs D-IC#1 and D-IC#2 are equipped in the panel 10 and each of the data driver ICs respectively outputs 2880 data voltages to 2880 data lines, 2880 channels CH are formed in the DAC 33 configuring each of the data driver ICs. Each of the channels CH generates one data voltage corresponding to one piece of digital image data.
In this case, the gamma voltage generator 35 generates eight gamma voltages RG1 to RG8 for pieces of image data corresponding to a red pixel, eight gamma voltages GG1 to GG8 for pieces of image data corresponding to a green pixel, and eight gamma voltages BG1 to BG8 for pieces of image data corresponding to a blue pixel, and supplies the generated gamma voltages to the DAC 33.
As described above, the gamma voltages are generated by the two data driver ICs, and there is a process differential between the two data driver ICs. Therefore, although pieces of image data having the same level are supplied to the two data driver ICs, a fine difference occurs between images respectively output by the two data driver ICs.
For example, as illustrated in FIG. 1, when a display area 11 of the panel 10 is divided into two areas A and B and the two areas A and B are respectively driven by the two data driver ICs, although pieces of image data having the same level are supplied to the two data driver ICs, a difference occurs between images respectively output by the two areas A and B.
To provide an additional description, since the gamma voltages are separately generated by the two data driver ICs, block dim occurs in the panel 10, and a uniformity of the panel 10 is reduced.